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Conduit Capacity Chart


Conduit Capacity Chart
Conduit Capacity Chart
Conduit Capacity Chart
How to Use Selector
The maximum number of cables that each conduit size may contain to conform with National Electric
Code Standards are given below. To find the conduit size required for cables where the O.D. is not shown
and for combinations of different size cables, follow these steps:
1. Square the O.D. of each cable and total the results.
2. Multiply the total by .7854. This is the total area of the cables in square inches. (See note.)
3. From Actual Area (*), select a conduit size with area equal to or greater than the total area.
NOTE: Actual area to be occupied (sq. in.) National Electric Code Standard based on 40% fill applies to
installation of 3 or more cables in a conduit. A single cable is permitted to occupy 53% and two cables are
limited to 31% conduit fill. For a singles cable, use .5927 in step 2; for two cables, use 1.0134; for three or
more cables, use .7854.
Installation Suggestions
This chart is based on the maximum number of cables permitted in conduit under the National Electric
Code, and is calculated on the area of the cables with 40% of the conduit filled. *For conduit runs of 50 to
100 feet, the installed number should be reduced by 15%, or use the next size larger conduit. Each 90°
conduit bend may be estimated as equal to the friction of 30 feet of straight level conduit. If more than two
90° bends are to be used in the conduit run, or if the run is to be over 100 feet in length, insert a pull box.
The use of anti-friction agents is recommended during pulling operations.
Caution: Be sure the anti-friction agent selected is compatible with the cable jacket material. (Check the
label.)
Installation Tips
In general, high and low level signals (mike and speaker wire, telephone and speaker wire) should never
be run in the same conduit without obtaining engineering advice. Unshielded 300 ohm antenna lead-in
wire should not be run in metallic conduits. The national Electric Code forbids the installation of
communication cables in the same conduit with power cables.
Pulling Tensions
Annealed copper will begin to permanently elongate (stretch) under a stress of approximately 15,000
lbs./sq. in. The following table lists the absolute maximum recommended pulling tensions for specific
conductor sizes. For multi-conductor cables, multiply the appropriate value by the total number of
conductors. During installation the total pulling tension must be equally distributed among all conductors.
24 AWG - 4 lbs.
22 AWG - 7 lbs.
20 AWG - 12 lbs.
18 AWG - 19 lbs.
16 AWG - 30 lbs.
14 AWG - 48 lbs.
12 AWG - 77 lbs.
Conduit Capacity Chart
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